Why does metadata have to stored in table cells according to Codd's 12 rules

Among Codd's 12 rules for Relational Database Management Systems is Rule 1, which states the following: > **Rule 1**: Information rule > > All information(including metadata) is to be > represented as stored data in cells of tables. The rows and columns > have to be strictly unordered. Why is it important that metadata be stored in tables?